The Arctic is a sentinel of global change. This region is influenced by multiple physical and socio-economic drivers and feedbacks, impacting both the natural and human environment. Air pollution is one such driver that impacts Arctic climate change, ecosystems and health but significant uncertainties still surround quantification of these effects. Arctic air pollution includes harmful trace gases (e.g. tropospheric ozone) and particles (e.g. black carbon, sulphate) and toxic substances (e.g. polycyclic aromatic hydrocarbons) that can be transported to the Arctic from emission sources located far outside the region, or emitted within the Arctic from activities including shipping, power production, and other industrial activities. This paper qualitatively summarizes the complex science issues motivating the creation of a new international initiative, PACES (air Pollution in the Arctic: Climate, Environment and Societies). Approaches for coordinated, international and interdisciplinary research on this topic are described with the goal to improve predictive capability via new understanding about sources, processes, feedbacks and impacts of Arctic air pollution. Overarching research actions are outlined, in which we describe our recommendations for 1) the development of trans-disciplinary approaches combining social and economic research with investigation of the chemical and physical aspects Arctic air pollution: Challenges and opportunities for the next decade of Arctic air pollution; 2) increasing the quality and quantity of observations in the Arctic using long-term monitoring and intensive field studies, both at the surface and throughout the troposphere; and 3) developing improved predictive capability across a range of spatial and temporal scales. Domain Editor-in-Chief

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Recent attention to the role of Indigenous knowledge (IK) in environmental monitoring, research and decision‐making is likely to attract new people to this field of work. Advancing the bringing together of IK and science in a way that is desirable to IK holders can lead to successful and inclusive research and decision‐making. We used the Delphi technique with 18 expert participants who were IK holders or working closely with IK from across the Arctic to examine the drivers of progress and limitations to the use of IK along with science to inform decision‐making related to wildlife, reindeer herding and the environment. We also used this technique to identify participants' experiences of scientists' misconceptions concerning IK. Participants had a strong focus on transformative change relating to the structure of institutions, politics, rights, involvement, power and agency over technical issues advancing or limiting progress (e.g. new technologies and language barriers). Participants identified two modes of desirable research: coproducing knowledge with scientists and autonomous Indigenous‐led research. They highlighted the need for more collaborative and coproduction projects to allow further refinement of approaches and more funding to support autonomous, Indigenous‐led research. Most misconceptions held by scientists concerning IK that were identified by participants related to the spatial, temporal and conceptual scope of IK, and the perceived need to validate IK using Western science. Our research highlights some of the issues that need to be addressed by all participants in research and decision‐making involving IK and science. While exact approaches will need to be tailored to specific social‐ecological contexts, consideration of these broader concerns revealed by our analysis are likely to be central to effective partnerships. A free Plain Language Summary can be found within the Supporting Information of this article.

Effective responses to rapid environmental change rely on observations to inform planning and decision-making. Reviewing literature from 124 programs across the globe and analyzing survey data for 30 Arctic community-based monitoring programs, we compare top-down, large-scale program driven approaches with bottom-up approaches initiated and steered at the community level. Connecting these two approaches and linking to Indigenous and local knowledge yields benefits including improved information products and enhanced observing program efficiency and sustainability. We identify core principles central to such improved links: matching observing program aims, scales, and ability to act on information; matching observing program and community priorities; fostering compatibility in observing methodology and data management; respect of Indigenous intellectual property rights and the implementation of free, prior, and informed consent; creating sufficient organizational support structures; and ensuring sustained community members’ commitment. Interventions to overcome challenges in adhering to these principles are discussed.